docs(styles): strip decorative comment banners from app.css

Replace ASCII-art separators (====, box-drawing rules, ---- dashes) with
plain section labels and rewrite the casual one-liners as terse, factual
comments.

src/app/styles/app.css

@@ -217,9 +217,7 @@
   /* Monospace label tracking — used in Loader and Footnote */
   --tracking-wider-mono: 0.2em;
 
-  /* ============================================
-     SHADOW TOKENS
-     ============================================ */
+  /* Shadow tokens */
 
   /* Default resting shadow — equivalent to Tailwind's shadow-sm. Used on
      buttons, sliders, popover triggers in non-floating state. */
@@ -246,9 +244,7 @@
   /* Drawer / overlay shadow — full-strength shadow-2xl. */
   --shadow-overlay: 0 25px 50px -12px rgb(0 0 0 / 0.25);
 
-  /* ============================================
-     MOTION TOKENS
-     ============================================ */
+  /* Motion tokens */
 
   --duration-fast: 150ms;
   --duration-normal: 200ms;
@@ -326,9 +322,7 @@
   }
 }
 
-/* ============================================
-   DESIGN-SYSTEM UTILITIES
-   ============================================
+/* Design-system utilities.
    Defined via `@utility` (Tailwind v4) so they integrate with the variant
    system (`hover:`, `dark:`, breakpoints) and don't rely on `@apply`
    chains. Colors reference the mode-switching semantic vars defined in
@@ -363,7 +357,7 @@
   }
 }
 
-/* ── Surface utilities ────────────────────────────────────────── */
+/* Surface utilities */
 
 @utility surface-canvas {
   background-color: var(--color-surface);
@@ -392,7 +386,7 @@
   border: 1px solid var(--color-border-subtle);
 }
 
-/* ── Shape / layout ───────────────────────────────────────────── */
+/* Shape / layout */
 
 @utility flex-center {
   display: flex;
@@ -423,7 +417,7 @@
   background-size: 10px 10px;
 }
 
-/* ── Typography ───────────────────────────────────────────────── */
+/* Typography */
 
 @utility text-label-mono {
   font-family: var(--font-primary);
@@ -432,7 +426,7 @@
   text-transform: uppercase;
 }
 
-/* Global utility - useful across your app */
+/* Honor prefers-reduced-motion: collapse animation and transition timing. */
 @media (prefers-reduced-motion: reduce) {
     * {
         animation-duration: 0.01ms !important;
@@ -441,12 +435,12 @@
     }
 }
 
-/* Performance optimization for collapsible elements */
+/* Hint the upcoming height animation on open collapsibles. */
 [data-state="open"] {
     will-change: height;
 }
 
-/* Smooth focus transitions - good globally */
+/* Transition siblings of a focus-visible peer. */
 .peer:focus-visible ~ * {
     transition: all 150ms cubic-bezier(0.4, 0, 0.2, 1);
 }
@@ -473,11 +467,9 @@
     animation: nudge 10s ease-in-out infinite;
 }
 
-/* ============================================
-   SCROLLBAR STYLES
-   ============================================ */
+/* Scrollbar styling */
 
-/* ---- Modern API: color + width (Chrome 121+, FF 64+) ---- */
+/* Standard API: color + width (Chrome 121+, Firefox 64+). */
 @supports (scrollbar-width: auto) {
     * {
         scrollbar-width: thin;
@@ -489,8 +481,8 @@
     }
 }
 
-/* ---- Webkit layer: runs ON TOP in Chrome, standalone in old Safari ---- */
-/* Handles things scrollbar-width can't: hiding buttons, exact sizing    */
+/* WebKit fallback: applies on top of the standard API in Chrome, standalone in
+   older Safari. Covers what scrollbar-width can't — hiding buttons, exact sizing. */
 @supports selector(::-webkit-scrollbar) {
     ::-webkit-scrollbar {
         width: 6px;
@@ -498,7 +490,7 @@
     }
 
     ::-webkit-scrollbar-button {
-        display: none;  /* kills arrows */
+        display: none; /* hide scrollbar buttons */
     }
 
     ::-webkit-scrollbar-track {